Conventional fixed winged aircraft are provided with a variety of aerodynamic control surface devices which include, for example, flaps, elevators, ailerons, trim tabs, and rudders. These control surface devices cooperatively operate to increase or decease lift over a given localized aerodynamic control surface for achieving pitch, yaw and roll control of the aircraft. These control surface devices are typically rigid structures which are rotatably attached to the wings or body (i.e., aerodynamic lifting surfaces) of the aircraft in a hinge-like fashion. Operation of the control surface devices typically forms gaps and/or abrupt changes in surface contours at or about the hinge line. Such gaps and abrupt changes are undesirable for a number of reasons. The gaps and abrupt changes tend to increase the radar signature of the aircraft, tend to increase aerodynamic drag, and give rise to the potentiality that foreign objects and/or debris may become caught thereat.
A classical aerodynamic control surface device includes a rudder which is hingedly attached to an aircraft vertical tail. Such a device configuration is highly aerodynamically efficient for providing directional yaw stability and control. In terms of radar cross section (RCS) signature, however, such configuration tends to undesirably increase the aircraft observability. In this respect, the vertical tail typically has a base portion which is attached to a topmost section of the aircraft fuselage or wing. At this base portion, the transition from the vertical tail to the fuselage or wing tends to create certain abrupt surface contour changes which increase the aircraft radar signature. In addition, the rotational attachment of the rudder to the vertical tail creates a hinge line which further increases the aircraft radar signature.
Some stealthy aircraft designs have avoided incorporation of the highly observable vertical tails in favor of less radar observable aerodynamic control systems. A contemporary example of such a design is the U.S. Military's B-2 bomber. These alternate designs may obtain direction control by means such as drag rudders at the wing tips or by thrust vectoring. While such control systems may have an associated mitigated radar signature, they also tend to be complex and not as aerodynamically efficient as the classic vertical tails.
It is therefore evident that there exists a need in the art for an aircraft aerodynamic control system which tends to be aerodynamically efficient while mitigating aircraft radar cross section signature by mitigating in comparison to conventional control designs.